Field Measurements of Grout Pressures During Tunnelling of the Sophia Rail Tunnel

During drilling, grout pressures were recorded on a tunnel lining measuring 9.5 m in diameter. Two tunnel rings were fitted with pressure gauges (14 gauges per ring). Measurements were performed for more than one day. Final hardening of the grout did not occur during this time. The lowest pressures were measured at the start of the drilling process after completion of the ring. Results show that the grout pressure distribution is dominated by injection during drilling, but this distribution changes when drilling stops and buoyancy forces start to exert an influence. The influence of buoyancy forces increases further away from the injection points. Bending moments in the tunnel lining also influence the gradient in the grout pressure distribution.